Project Summary: Although most of the transcripts produced from the human genome do not encode for proteins, the vast majority of non-coding RNAs remains completely understood. A newly appreciated class of non-coding RNAs are circular RNAs (circRNAs). In both Drosophila melanogaster and mice, circRNAs tend to emanate from genes with known neural functions and their expression is enriched in neural tissue. This suggests they might have functions in the nervous system. Recent work has found thousands of circRNAs to be expressed in mice and Drosophila; however, their functional relevance has only started to be explored. In Drosophila, we found that hundreds of circRNAs accumulate during normal aging in the fly head. Drosophila is a powerful system to study aging and age-related disorders of the nervous system. We hypothesize that this progressive accumulation of circRNAs in the brain contributes to age-related decline in neural function. Preliminary data shows that circRNA accumulation during aging can be modulated by environmental stresses, including temperature and caloric intake- all conditions that can modulate lifespan in Drosophila. In Aim 1 we propose to characterize the regulation of circRNAs globally during biological aging in brain neurons using RNA-seq analysis. In Aim 2, the functional elements enriched in age-accumulated and X16 regulated circRNAs will be investigated. Finally, in Aim 3, the function of X16 suppression of ank2 circRNA will be investigated by assessing lifespan, neuromuscular junction morphology and heat stress resistance. Preliminary data shows that circRNAs accumulated during aging in other organisms, including mice, making it likely that this accumulation also occurs in the human brain. Insights into the mechanism of circRNA accumulation during aging gleaned from Drosophila will thus likely be applicable to understanding circRNAs in the human brain. Given the health impact of age-related neurodegenerative disease in the US population it is important to understand the fundamental biology of this novel class of RNAs with likely functions in the aging brain.